1. Field of the Invention
The present invention relates to an electronic device having a structure in which an electronic component element is housed within a space formed by an element loading member and a lid member, and to a glass sealing method used when manufacturing the electronic device.
2. Description of the Related Art
In general, an electronic device is used for an electronic apparatus. Particularly, a crystal device as an example of the electronic device is used often for the electronic apparatus such as a mobile communication apparatus. For example, JP No. 3811423 (Patent Document 1) discloses a crystal device in which an element loading member and a lid member are joined by a glass sealing material, and a crystal vibration element as an electronic component element is housed within the space.
A crystal device 90 of a related technique shown in FIG. 7 includes an element loading member 92, a lid member 93, a crystal vibration element 94, a glass sealing material 95, and an activated brazing material 96. The element loading member 92 and the lid member 93 are joined by the glass sealing material 95, and the crystal vibration element 94 is hermetically sealed inside a space 91 formed by the element loading member 92 and the lid member 93. The lid member 93 is formed with metal, and the element loading member 92 is formed with ceramics.
A glass sealing method used when manufacturing the crystal device 90 is as follows: metal plating is applied on the lid member 93; the activated brazing material 96 is applied thereon; the glass sealing material 95 is applied thereon further; the lid member 93 is superimposed on the element loading member 92 on which the crystal vibration element 94 is loaded; and the glass sealing material 95 is melted by applying heat in an atmospheric pressure atmosphere to join the lid member 93 and the element loading member 92. The reason for providing the activated brazing material 96 between the lid member 93 and the glass sealing material 95 is for improving the joint strength between the lid member 93 and the element loading member 92.
The activated brazing material 96 is formed on the lid member 93 by a method described below, for example. First, a paste-type brazing material containing one or more kinds of activated metals selected from titanium, zirconium, and hafnium is printed on the joint faces of the lid member 93 and the glass sealing material 95 in a thickness of about 70 μm by screen printing, calender rolling, or the like. Then, after drying the printed paste-type brazing material containing the active metal, it is heated for 60 minutes at a temperature of about 800° C. in a heat treatment furnace of a reduced atmosphere. Thereby, the activated brazing material 96 in a layer thickness of about 55 μm is formed. At that time, a hydride layer of the activated metal in a film thickness of about 3 μm is formed on the surface of the activated brazing material 96.
As described above, with the crystal device 90 of the related technique, it is necessary to provide the activated brazing material 96 between the lid member 93 and the glass sealing member 95 for having the sufficient joint strength between the lid member 93 and the element loading member 92. However, for forming the activated brazing material 96, not only the price of the raw materials thereof is high but also the exclusively-used screen printing equipment as well as the heat treatment furnace of a reduced atmosphere is required. In addition, a high-temperature and long-time heat treatment is required at about 800° C. for 60 minutes. Thus, the use of the activated brazing material 96 complicates the manufacturing steps and increases the manufacturing cost.
It is therefore an exemplary object of the present invention to provide an electronic device and a glass sealing method used therefor, with which a sufficient joint strength can be acquired only with the use of a glass sealing material without using an activated brazing material.